Typed Scheme: A Brief Introduction for PLT Scheme Programmers

Sam Tobin-Hochstadt

December 14, 2006

Typed Scheme is a Scheme-like language, with a type system that
supports common Scheme programming idioms. Explicit type declarations
are required — that is, there is no type inference. The language
supports a number of features from previous work on type systems that
make it easier to type Scheme programs, as well as a novel idea dubbed
“occurrence typing” for case discrimination.

Typed Scheme is also designed to integrate with the rest of your PLT
Scheme system. It is possible to convert a single module to Typed
Scheme, while leaving the rest of the program unchanged. The typed
module is protected from the untyped code base via
automatically-synthesized contracts.

There is no need to specifically install Typed Scheme. Simply running
one of the example programs described in this manual will
automatically download and install the necessary software. However,
it can also be installed from the MzScheme or DrScheme prompt with the
following command: